Adapted invariant measures, such as the natural area measure
(Liouville), have a central place in the development of the ergodic
theory for billiards. These measures ensure local Pesin charts may be
constructed almost everywhere even in the nonuniformly hyperbolic
setting. Recently, for Sinai billiards satisfying certain conditions,
the unique measure of maximal entropy has been shown to be adapted.
However, not all positive entropy measures are. To investigate the
connection between entropy and adaptedness, I will discuss Markov
interval maps with exactly one singularity. I will show that a
condition relating the entropy of the map and the “strength” of the
singularity determines if the measure of maximal entropy is adapted. I
will also show that under a Hölder condition, recurrence of the
singularity is necessary to have nonadapted invariant measures.
|